This invention relates to known apparatus in which control of the composition of the operating mixture of an internal combustion engine is provided with a fuel apportioning device, the fuel supply line of which leads from a fuel feed device that supplies fuel at an essentially constant pressure and is arranged to include a throttle valve actuatable by means of an air metering member of the fresh air quantity conducted to the internal combustion engine. Also, in this device the uncontrolled pressure chamber of a differential pressure valve lies downstream of the fuel apportioning device, and a relief line containing a throttle means leads from the controlled pressure chamber lying upstream of the apportioning device, with the relief line being connected to the working chamber of a positioning motor upstream of the throttle.
It is known with such apparatuses that during sizable and fast correction movements of the positioning motor, the essentially constant pressure within the fuel supply line upstream of the apportioning device can no longer be maintained constant, because the output of the fuel feed apparatus is too low and for the reason that under some circumstances an intermittent output then causes additional disadvantages. The fuel pressure which serves in such known apparatuses not only for setting the differential pressure at the cross-sectional apportionment area but also for the creation of a restoring force upon an air metering device displaceable by means of the differential pressure in the intake air flow of the combustion engine must, however, be kept constant to within desired modulating variations in order to maintain the required composition of the operating mixture of an internal combustion engine. A pressure drop occurring during a large adjustment of the positioning motor also further increases the dead period of the control apparatus disadvantageously.